The present invention relates to a belt drive system, and more particularly, the present invention relates to a belt drive system including a pulley assembly and tension apparatus.
Many existing vehicles (e.g., automobiles, tractors, straight trucks, tractor-trailer combinations, etc.) include power transmission belt drive systems to transfer power from an engine or motor to one or more auxiliary or accessory components. For example, in vehicular applications, these accessories can include power steering pumps, water pumps, air conditioning compressors, fuel pumps, and alternators. Generally, each accessory includes a pulley that is coupled to pulleys of other accessories via one or more belts. Belt drive systems can be used in conjunction with the primary engine or motor of a vehicle to transfer power via pulleys and belts to one or more accessories, or these systems can be used in conjunction with auxiliary systems (e.g., refrigeration systems for transport refrigeration units, etc.) to transfer power.
In most belt drive systems, one or more components are movable such that the belt can be assembled onto or trained around the pulleys. In some vehicles, the belt drive system is located in a relatively small compartment, and as a result, the components of the belt drive system are positioned relatively close to each other. Often, no tension can be placed on the belt when the belt is trained onto the pulleys due to the confined space in which the belt drive system is located. In some existing belt drive systems, the belt must be rotated about a point to fit the belt onto the pulleys. In other existing belt drive systems, the belt is slid in a slot. However, these belts often have inadequate tension upon assembly onto the pulleys and other components of the belt drive system interfere with the belt during assembly, which makes the process time consuming and difficult.
In many belt drive systems that include an alternator, the alternator is mounted in a slot for linear movement, or is pivoted on one end so that the alternator can move in an arc having a radius that is the same as the alternator length. In these systems, the alternator has one degree of motion (i.e., either sliding movement or rotational movement), and the belt is trained around the pulleys of other components in the belt drive system before being trained onto the alternator pulley. Often, the belt has at least some tension prior to assembly onto the alternator pulley, making the process of training the belt onto the pulleys somewhat difficult. After the belt has been trained onto all of the pulleys, the alternator is moved linearly or pivoted to extend or tighten the belt. Other systems move the engine or motor, or another component of the system, to attach the belt to the pulleys. Many of these systems use bolts to pull or push the belt with different components. However, in relatively small compartments, simply moving or pivoting one or more components interferes with other components (e.g., a compressor, a fan pulley, etc.) in the system.
Typically, the belt must be tightened or tensioned after the belt is trained onto or connected to the pulleys so that power can be efficiently transferred among the accessories. In order for the belt drive system to function, the belt must be maintained at a predetermined tension to avoid shortening the life of the belt or the components of the system. Some belt drive systems include an automatic tensioner device that presses on the belt, which acts to lengthen the distance about which the belt is trained and thereby causes the belt to be extended or in tension. Various techniques and geometries have been employed to provide the biasing force. However, for belt drive systems in relatively small compartments, there is no room for an automatic tensioner device.
Some belt drive systems use stretch belts that typically do not require movable pulleys, and when stretched properly, will maintain tension for a given period. However, these belts generally cannot be fully stretched upon initial assembly onto the pulleys because the high belt tension needed causes too much bearing stress on the belt. Similarly, too little tension or stretching of the belt results in the belt being too loose to adequately transfer power between the components of the belt drive system.
Typically, adjusting and measuring the tension on a belt is difficult due to very little room for accessing the belt within the compartment. In existing belt drive systems, the process of adjusting and measuring the tension is often repeated several times to achieve a desired result. Also, special, often costly tools are often required to adequately measure the belt tension. However, these tools often provide inconsistent readings and when combined with existing belt drive systems, can significantly increase the time needed to assemble the belt onto the pulleys.